In four-stroke internal combustion engines, the power dissipated in the thermodynamic cycle of an air-fuel mixture is harnessed by the linear motion of a piston. A connecting rod translates this linear motion of the piston into the rotary motion of the crankshaft. This conversion of motion is applied to derive useful work that is later transferred into different drive mechanisms.
Having a longer piston stroke helps in achieving a higher compression ratio of the working substance. This is desirable as it produces better thermodynamic efficiency in low speed engines and a much higher power output in high speed engines. However, as the conventional connecting rod is a single link mechanism, the length of the stroke is limited due to geometrical limitations when the connecting rod may come in contact with the side wall of the cylinder in which the piston reciprocates. Lengthening the connecting rod is not an option in many cases as it complicates the design of the engine by making it bulky and a lot heavier, which usually renders moot the design trade-off.
In some prior multi-link engine designs, the designs subject the components to high tension and stress conditions while providing little gain in useful work compared to conventional engine designs. In other prior multi-link engine designs, the designs include a complex mechanism with an increased number of linkage members and a linkage activation assembly.
A need remains for improved internal combustion engine linkage systems that overcome the drawbacks of conventional designs and offer optimized thermodynamic efficiency for use with modern fuels and multiple engine applications.